Novel solvents and reaction conditions for the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

Abstract

2,5-Furandicarboxylic acid (FDCA) is an important biomass-derived monomer for the production of sustainable materials and bioplastics. Upgrading FDCA to polymers could effectively replace petroleum-derived plastics, reducing carbon emissions and reliance on fossil fuels while also improving the material properties of the final products. However, FDCA production is not economically viable in its current form. In this dissertation, two critical challenges to FDCA production are addressed: (1) its poor solubility in most solvents, which complicates separations and purification processes and (2) the limited understanding of how solvent selection influences the oxidation reaction to produce FDCA. To do so, FDCA solubility was systematically assessed in a range of organic solvents and aqueous/organic solvent blends. Solubility data was correlated first to the Hansen Radius of Interaction (Ri,j) parameter, allowing for optimization of blend ratios, and then more deeply to fundamental molecular properties, structures, and thermodynamic behaviors. Solubility behavior was found to be correlated with the type of solvent, specifically alcohol or non-alcohol, with the impact of factors like capacity for hydrogen bond formation, strength of London dispersion forces, and molecular polarity differing based on solvent type. These findings were used to develop artificial neural network models for solubility prediction. Solubility rankings were also correlated to excess enthalpy values for mixed solvent systems, where more negative excess enthalpies correlated to higher solubility. A select group of solvent blends were assessed for FDCA production in batch reactors using a commercial 5% Pt/C catalyst. The effects of solvent choice, initial reactant concentration, and temperature on reaction yields were examined in detail. Solvent degradation at reaction conditions was also investigated. Mixtures of sulfolane and water were found to balance FDCA yields, initial reactant concentration, and solvent robustness most effectively out of the solvents studied. Connections to prior upstream work in the conversion of biomass to FDCA precursor 5-hydroxymethylfurfural also suggest potential for a combined biomass-to- FDCA system. Finally, a comprehensive review of recent literature highlights paths forward for future research.